During the Middle Ages, porpoises were called mereswines, or 'sea pigs'. In those days, they were consumed a lot. There was a huge population living along the Dutch coast. Those were the days when anchovies and other small fatty fish were plentiful. The porpoises followed the fish into harbors, which is why they are officially called harbor porpoises. Porpoises grew scarcer halfway through the 20th century, however the number of sightings since 1995 have increased tremendously. The porpoise is presently the most common cetacean in the North Sea.